1. Field of the Invention
The present invention relates to an acrylic elastomer composition, and more particularly a carboxyl group-containing acrylic elastomer composition having an improved scorch resistance.
2. Description of Related Art
Acrylic elastomers have been so far widely used as vulcanization molding materials for sealing materials, hoses, electrical parts, etc. owing to their distinguished heat resistance, oil resistance, etc. In acrylic elastomers for use as such vulcanization molding materials, physical properties of vulcanization products largely depend on kinds of cross-linkable monomers in copolymerization or on kinds of cross-linking agents.
For example, when acrylic elastomers containing cross-linking site monomers having a double bond are vulcanized with sulfur (donor), the resulting vulcanization products are poor in heat resistance and weathering resistance because of the presence of unsaturated bonds in the molecule, and mold corrosion due to sulfides formed during the vulcanization is observable, though a high vulcanization speed can be attained. Acrylic elastomers containing epoxy groups as crosslinking sites have not only a low vulcanization speed, but also suffer from considerable changes in normal state physical properties due to the secondary vulcanization and are also poor in heat resistance and compression set characteristics.
Acrylic elastomers having carboxylic groups as crosslinking sites are generally subjected to amine vulcanization, and the resulting vulcanization products are distinguished in normal state physical properties, compression set characteristics, etc., but still have such a disadvantage as a short scorch time. To improve the productivity an injection molding process has been now widely used, where the scorch resistance is one of very important characteristics and thus a longer scorch time is now in increasing demand.